Developing composition.



THEODORE (1T. BREWSTER, OF CHESTER, PENNSYLVANIA.

DEVELOPING COMPOSITION.

To all whom it may concern:

Be it known that l, Tmononn J. BREW- STER, a citizen of the United States, residing at Chester, in the county of Delaware and State of Pennsylvania, have invented certain new and useful Improvements in Developing Compositions, of which the following is a specification.

My invention relates to improvements in developing compositions, the object of the invention being to provide a developing composition which prevents any possibility of over developing, but insures the bringing out of the detail of the pictures regardless of the exposure, assuming such exposure to be anywhere within any reasonable limits.

The object of my invention is to prevent the phenomena known as reversal of image due to overexposure, and to lengthen the time of exposure of photographic emulsions to light whereby recordable results may be obtained by developing said prolonged exposed emulsions in a bath composed of para phenylene diamin, sodium sulfite, sodium nitrite, sodium carbonate and water, in stead of ordinary well known developing compositions which do not make available the full desirable range of exposures, it being well known that many photographs are imperfect because the portions in deep shadow do not show in the photograph through underexposure although the brighter portions are sufliciently exposed, whereas if the exposure had been timed so that the portions in deep shadow would show, the brighter portions would be ruined by overexposure, presuming that ordinary developing compositions had been used. However with my improved composition it is possible to expose many times as long without injury to the result.

The invention relates to the use of certain types of chemical compositions for the purpose of developing photographic plates, films, papers, lantern slides, and the like, whereb distinctive advantages can be secured that are not secured by chemical compositions in general use for the purpose. In using this phrase types of chemical compositions, I use it in the broad sense to include any chemical composition having the specific properties to perform the functions enumerated below, which can be ac- Specification of Letters Patent.

Patented Feb. 5, 191%.

Application filed February 25, 1915. Serial No. 10,601.

complished with my improved composition:-

1. Development of photographic image is to be substantially complete.

2. Development of photographic image is to be limited to chemical action upon the sensitized material at the portions represented by the image, and not to proceed to any appreciable extent at the portions of the sensitized material upon which there was no image. I use the word appreciable to indicate an extent which would result in a harmful efiect when used for the purpose intended.

-3. Development of the photographic image is to proceed in intensity in accordance to the strength of the image or function thereof in accordance to the above enumerated funotionsand conditions.

To briefly summarize the action of compositions for the purpose in general use, I give below what I believe to be a correct statement concerning such compositions:-

1. Certain compositions induce chemical action to a greater or less degree in the portions of the sensitized material in which no image so projected by means of light, thus resulting in the production of what is known as chemical fog.

2. Certain compositions induce an exaggerated development in the portions of the image of greatest illumination, thus altering the contrasts of light and shadow to such an extent that printing from such negatives is difiicult, and at times impossible to secure a good result, without the use of special methods or the use of special sensitized printing material, which mvolves labor, expense, and delays, and which at best is uncertain.

3. Certain compositions fail to induce chemical action to an appreciable extent in the portions of the image of least illumination, whereby the resulting negative cannot be intensified to the point where a good printing can be secured without sacrificing either extreme of light and shadow.

4. Certain compositions Work well when the exposure is made within a certain time limit, which is usually narrow, hence good I being obtained when the exposure was not in accordance with the developing composition.

When developing subjects of great contrasts, such as waterfalls in bright sunlight, portions of the image representing dense shadows, the character of the developing composition is of great importance for in such cases it is very easy to over expose the most illuminated portions of the image in order to secure an appreciable development in the least illuminated portions. Pictures of this type are usually failures unless ray filters are used or other means taken to secure a better result.

5. Certain chemical compositions work best with one or more brands or types of image producing films, plates, etc., and are therefore limited in their use.

6. Certain compositions, in some cases, develop such great density in the negative that printing is extremely difficult.

7. Certain compositions which contain alkalis in large amount cause a swelling or disintegration of the gelatin base .of the film, aberration of the image, abrasion marks, stains, frilling of the film at the edges, and discomfort to the operator.

My improved composition is intended to overcome the above enumerated defects .of compositions for the purpose in general use, and make it possible to secure substantially perfect results Within an enormous range of exposure, thus permitting the amateur, who usually does not understand or fails to realize what constitutes a normal exposure, to secure a perfect printing negative from practivally each exposure he makes. While the amateur is still able with the usual equipment to both over and under expose his pictures, the use of my composition renders his working latitude so great that it is impomible for him to secure a poor'result if he exercises a small amount of judgment.

Owing to the circumstances and conditions underwhich motion-pictures are taken and finished, when using the present equipment and chemical compositions, many subjects are impossible to reproduce successfully owing to the degree of under exposure in all or any part of the subject, or the opposite tendency due to over exposure in portions of the picture. However, with my composition these subjects can be reproduced substantially perfect, especially in the cases where the exposures are made in accordance with the mostelfective range of efliciency of the particular composition used in development.

Having described where my chemical comone may determine whether' a given sub' stance possesses these properties, and its range of effectiveness, and finally present a theory which will cast light upon the chemical principles involved.

In my improved composition, I use as an active ingredient, para phenylene diamin, with or without a preservative such as sodium sulfite, with a catalyst such as sodium nitrite, with or without an alkali such as sodium carbonate dissolved in water. Such a composition possesses the properties to a certain extent depending upon the actual composition and physical conditions under which it is used as are described in the foregoing.

Para phenylene diamin has an action upon exposed photographic plates which results in developing out the latent image.

I have found by actual experiment that the composition given below produces splendid results Para phenylene diamin 10 grains Sodium sulfite 10 grains Sodium nitrite 10 grains Sodium carbonate 2 grains Water 8 ounces and I offer the following theory to explain its peculiar action.

The action of light renders silver bromid an oxidizing agent with respect to the developer. If two or more phenolic groups, with or without substitution, or one phenolic group and one or more other reactive groups, such as amino groups are present, two of which are in the ortho or para position with respect to each other, on oxidation by means of the light affected silver bromid, products are formed in greater or less amount which at least in the nascent state arecapable of reducing light-unaffected silver bromid, and thus produce exaggerated densities.

' Doubtless on development, such substances as pyrogallic acid, hydroquinone, pyrocatechin, etc., form compounds which in the nascent state are so reactive that'their ring formation or structure is completely broken down, whereas para phenylene diamin, by reason of its two amino groups, its para positlon, its simple benzene nucleus, and its few and simple oxidation products formed on development, is chemically incapable of inducing the development of an image of greater density than the exposure warrants,

or of inducing development where no light had acted upon the emulsion. These properties,-together with its keeping properties, easy manufacture, relative high solubility in water, non-requirement of alkali to functionate, non-staining and fogging properneaaaoe r ties, and finally the enormous range of exposure possible to develop properly, render its substance a most suitable developer.

ll do not limit my invention to the development of photographic plates or films, but include also other forms of image producing materials such as photographic printing papers,

I may also vary the composition by the addition of contributary ingredients, and in some cases it may use the active ingredient alone in various proportions or mixtures of various active ingredients with or without the contributary ingredients, and thus secure variousefiects, hence it would have it understood that the composition is capable of modification according to the use, as for example, for the purpose of developing either initially or completing the develop ment, and I may use the composition in connection with other compositions to secure the desired efiects,

in carrying out my invention any chemical composition can be used for the purpose of development of photographic images, possessing the distinctive features substantially as described, included in the following types of chemicals :derivatives or benzene and its homologues and other cyclic nuclei containing at least two reactive groups in ortho or para position with or without substitution in the unreactive group including para phenylene diamin.

llhus in carrying out my invention it may use organic substances or inorganic substances capable oi reaction of light unatfected sensitized material, and not reactive with light unafi'ected sensitized material,

Having thus described my invention, what it claim as new and desire to secure by Let ters Patent is:

l, A developing composition containing paraphenylenediamin as an active ingredient, combined with a catalyst and water, substantially as described.

2.. A developing composition containing as an active ingredient para phenylene diamin, combined with a preservative, a catalyst, and water, substantially as described 3. A developing composition containing as an active ingredient para phenylene diamin, combined with a pres arvative, sodium nitrite, an alkali, and water, substantially as describedw 4a A developing bath for prolonged exposed emulsions ot the character described, composed of para phenylene diamin, sodium sulfite, sodium nitrite, sodium carbonate, and water, substantially as described.

in testimony whereof l have signed my name to this specification in the presence of two subscribing witnesses.

THEQDORE J. BREWSTER.

Witnesses:

Sinner W. BREWSTER, S. W. Fos'rnn till till 

